1. Field of the Invention
The present invention relates generally to the field of reciprocating pumps, and more particularly to a bi-directionally driven reciprocating pump which is driven by energization of solenoid coils and is particularly well suited to pumping fluids such as fuel in injection systems.
2. Description of the Related Art
A wide variety of pump designs and styles have been devised and are presently in use. In general, pumps are based upon the principal that fluid can be drawn into a pumping volume under a first pressure, and expelled from the pumping volume under a higher pressure to displace the fluids are desired. Depending upon the specific application envisaged, pumps are typically selected as a function of their displacement, cycling characteristics, pressure ratings, size, and so forth. Moreover, pumps are typically classified by their general nature, such as reciprocating or rotary, and by the nature of their driver, typically being designed to be electrically driven, or otherwise.
Specific pumps have been developed for demanding reciprocating applications such as fuel injection. In one design for this application, a reciprocating assembly, including an armature and a guide tube, are driven by energization of an electric solenoid. As the reciprocating assembly is moved into and out of a pump section, fluid is drawn into the pump section, and expelled therefrom under a higher pressure. The energization of the solenoid controls the pumping cycle, with the return stroke of the reciprocating assembly resulting from a spring bias of the reciprocating assembly toward a retracted position. Pumps of this type have been applied in combustion engine fuel injection systems due to their high performance and efficiency, their inherent electrical controllability, and to their reduced size.
While applications such as fuel injection have benefited from reciprocating pumps of the type described above, their continues to be a need for improved pumps for this and similar applications. For example, to serve high performance internal combustion engines, reciprocating fuel injection pumps require increasingly short cycle times and may benefit from additional flexibility in the control of the position and velocity of a reciprocating assembly. For example, if a pump assembly in an electrically driven reciprocating fuel pump could be cycled more rapidly, the engine designer could provide for increased flow rate of fuel into combustion chambers, as well as greater controllability of the quantity of fuel injected per stroke. This enhanced flexibility would permit for greater control and servicing of higher torque and higher horsepower engines. Even conventional engines could benefit from enhanced controllability of such pumps, and shortened cycle times.
There is a particular need, at present, for improved pumping techniques which can make use of electrical control signals to regulate the position and velocity of a reciprocating pumping assembly. This need is particularly felt in the area of fuel injection, where a pumping assembly may be directly secured to a pump driving assembly which receives the electrical control signals. In direct in-chamber injection applications, the resulting assembly may be affixed to one or more injection nozzles to provide a compact, high performance pump and injector system.
The present invention provides a bi-directionally driven reciprocating fluid pump technique designed to respond to these needs. The pump may be employed in a wide variety of applications, particularly in applications in which high-speed reciprocation is desired, with relatively low volumetric flow rates. The present technique is particularly well suited to fuel injection systems, in which a fuel is drawn into a pumping assembly from a source, pressurized in the pumping assembly, and injected for combustion in a combustion chamber, such as directly into a cylinder of an engine.
The technique of the invention makes use of a pair of reluctance gap coil arrangements within a drive section of a pump. Each coil can be energized to draw an armature of a reciprocating assembly towards a reluctance gap. The reciprocating assembly may be biased into a centered or normal position by springs. A guide tube acts as a pump plunger, and is reciprocally driven by cyclic energization of the coils. Fluid is drawn into a pump chamber as the guide tube is retracted from the pump chamber, and is pressurized and expressed from the pump chamber as the guide tube is extended into the pump chamber. Control signals to the coils may be timed and shaped to provide reduced cycle times and to vary volumetric flow rates from the pump, as well as to vary volumetric displacement per pump cycle.